Title: Early Age Restrained Shrinkage Strains in Slabs and Standard Drying Shrinkage Strains

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Publication: CIA

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Date: 2/14/2011

Abstract:
Crack prevention is often a critical parameter in the design and construction of ground and suspended concrete slabs. Often when the degree of restraint is high, uncontrolled cracking can influence the serviceability of a structure. Designers often use the specification of maximum values for standard 56-day drying shrinkage strains in an attempt to control cracking of concrete pavements. Previous research6,7 has shown that the development of tensile stresses, and hence the increased risk of crack formation and propagation, is linked to events that take place in the first four to six hours after placement. Other work has shown that the results from the AS1012.132 drying shrinkage test can be more variable than those for compressive strength data.8 In this paper, the results from an experimental program involving the construction and instrumentation of five slabs, made using concrete with nominal 56-day drying standard shrinkage strains ranging from 450 microstrain to 800 microstrain, are reported. The aim was to investigate the relationship between early age shrinkage, which is not measured in the standard drying shrinkage test, standard 56-day drying shrinkage strain values and actual strains in slabs.